6х-3 (5х+4)-2(7х-3)=-6
6х - 15х - 12 - 14х + 6 = - 6 - 23х = 12 х = - 12/23
5x-(6x-(7x-8x+9))= 5x-(6x-7x+8x-9)= 5x-6x+7x-8x+9= 9-2x